2017 Vol. 34, No. 11
2017, 34(11): 2385-2391.
doi: 10.13801/j.cnki.fhclxb.20170228.001
Abstract:
Carbon nanotubes-Si(CNTs-Si) Schottky solar cells have the advantages of low cost and facile fabrication. However, the applications of such devices have been limited by the low photovoltaic conversion efficiency, which is possibly derived from the high resistance of CNTs, non-uniform junction and serious light reflection. A composite film of poly(3,4-rethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS)-CNTs was prepared as a transparent conducting film for Si-based solar cell. The current-voltage curves show that the use of PEDOT-PSS considerably improves the conversion efficiencies from 5.9% for pristine CNTs-Si solar cells up to 11.6%. Aligned CNTs in the composite film facilitate the transfer of photo-generated holes in the junction region. The applied PEDOT-PSS conducting polymer fills the voids between nanotubes, improving the contact between CNTs and Si and forming additional Schottky junctions. A transparent polydimethylsiloxane (PDMS) film with an inverted pyramid structure was attached on the (PEDOT-PSS)-CNTs-Si solar cells, further improving the conversion efficiency to 12.4% by reducing light reflection loss. The electron beam induced current technique shows that the photo-conversion mechanism of such devices is based on a Schottky junction.
Carbon nanotubes-Si(CNTs-Si) Schottky solar cells have the advantages of low cost and facile fabrication. However, the applications of such devices have been limited by the low photovoltaic conversion efficiency, which is possibly derived from the high resistance of CNTs, non-uniform junction and serious light reflection. A composite film of poly(3,4-rethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS)-CNTs was prepared as a transparent conducting film for Si-based solar cell. The current-voltage curves show that the use of PEDOT-PSS considerably improves the conversion efficiencies from 5.9% for pristine CNTs-Si solar cells up to 11.6%. Aligned CNTs in the composite film facilitate the transfer of photo-generated holes in the junction region. The applied PEDOT-PSS conducting polymer fills the voids between nanotubes, improving the contact between CNTs and Si and forming additional Schottky junctions. A transparent polydimethylsiloxane (PDMS) film with an inverted pyramid structure was attached on the (PEDOT-PSS)-CNTs-Si solar cells, further improving the conversion efficiency to 12.4% by reducing light reflection loss. The electron beam induced current technique shows that the photo-conversion mechanism of such devices is based on a Schottky junction.
2017, 34(11): 2392-2400.
doi: 10.13801/j.cnki.fhclxb.20170220.002
Abstract:
The waterborne polyurethane (WPU) microfiber synthetic leather(PET-PA6/WPU)using segmented-pie microfiber nonwoven as the base and WPU membrane as the polymer coating was prepared through dry transfer-coating method. The method realized the greening preparation of microfiber synthetic leather. The structure and performance of PET-PA6 hollow segmented-pie microfiber nonwoven were firstly investigaed by FESEM, and then the effect of foaming ratio on the structure and performance of WPU membranes was systematically studied, finally the structure, air permeability, water vapor permeability and physical mechanical properties of PET-PA6/WPU were analyzed. The results show that the fiber diameter size of PET-PA6 hollow segmented-pie microfiber nonwoven is between 2.2-5.5 μm, and its performance meets the using demand of textiles-nonwoven for synthetic leather. When the foaming ratio is 100%, the structure of the obtained WPU membrane is dense, and its air permeability and water vapor permeability are 14.72 L/(m2·s) and 3 686.84 g/(m2·24 h), respectively. The WPU membrane exhibites connecting bubble hole and porous surface, and its mean pore size, air permeability and water vapor permeability increase with the increase of foaming ratio. When the foaming ratio is 250%, the air permeability and water vapor permeability are 169.43 L/(m2·s) and 5 209.09 g/(m2·24 h), respectively. The PET-PA6/WPU microfiber synthetic leather is in a three-layer configuration, including fabric layer, foam layer and surface layer. The air permeability of PET-PA6/WPU leather is 0.45 L/(m2·s), tensile strength of perpendicular and parallel are 138.40 N and 96.60 N, elongation at break of perpendicular and parallel are 72.70% and 101.80%, tear strength of perpendicular and parallel are 63.20 N and 88.20 N, peeling strength of before hydrolyze and after hydrolyze are 15.86 N and 15.61 N, and creasy recovery angle of perpendicular and parallel are 149.30° and 151.80°, which are better than knitting synthetic leather and real leather. The water vapor permeability of PET-PA6/WPU synthetic leather reaches 1 673.8 g/(m2·24 h) closing to real leather.
The waterborne polyurethane (WPU) microfiber synthetic leather(PET-PA6/WPU)using segmented-pie microfiber nonwoven as the base and WPU membrane as the polymer coating was prepared through dry transfer-coating method. The method realized the greening preparation of microfiber synthetic leather. The structure and performance of PET-PA6 hollow segmented-pie microfiber nonwoven were firstly investigaed by FESEM, and then the effect of foaming ratio on the structure and performance of WPU membranes was systematically studied, finally the structure, air permeability, water vapor permeability and physical mechanical properties of PET-PA6/WPU were analyzed. The results show that the fiber diameter size of PET-PA6 hollow segmented-pie microfiber nonwoven is between 2.2-5.5 μm, and its performance meets the using demand of textiles-nonwoven for synthetic leather. When the foaming ratio is 100%, the structure of the obtained WPU membrane is dense, and its air permeability and water vapor permeability are 14.72 L/(m2·s) and 3 686.84 g/(m2·24 h), respectively. The WPU membrane exhibites connecting bubble hole and porous surface, and its mean pore size, air permeability and water vapor permeability increase with the increase of foaming ratio. When the foaming ratio is 250%, the air permeability and water vapor permeability are 169.43 L/(m2·s) and 5 209.09 g/(m2·24 h), respectively. The PET-PA6/WPU microfiber synthetic leather is in a three-layer configuration, including fabric layer, foam layer and surface layer. The air permeability of PET-PA6/WPU leather is 0.45 L/(m2·s), tensile strength of perpendicular and parallel are 138.40 N and 96.60 N, elongation at break of perpendicular and parallel are 72.70% and 101.80%, tear strength of perpendicular and parallel are 63.20 N and 88.20 N, peeling strength of before hydrolyze and after hydrolyze are 15.86 N and 15.61 N, and creasy recovery angle of perpendicular and parallel are 149.30° and 151.80°, which are better than knitting synthetic leather and real leather. The water vapor permeability of PET-PA6/WPU synthetic leather reaches 1 673.8 g/(m2·24 h) closing to real leather.
2017, 34(11): 2401-2406.
doi: 10.13801/j.cnki.fhclxb.20170302.006
Abstract:
Calcium silicate-calcium alginate (CaSiO3-CaAlg) composite hydrogel plate films were prepared by calcium ion cross-linking the mixture of calcium silicate and sodium alginate, and their morphologies were observed. The CaSiO3-CaAlg film was characterized by FTIR, TG and XRD. The mechanical tensile properties of CaSiO3-CaAlg composite hydrogel films with different contents of CaSiO3 on the CaAlg were investigated under wet condition. The results show that the CaSiO3 and CaAlg have good compatibility and the addition of CaSiO3 can improve the thermal performance of CaAlg. With the increase of calcium silicate in CaSiO3-CaAlg composite hydrogel membrane, the limited stress first increases, and then decreases. The preparation of CaSiO3-CaAlg composite film is simple, without using any organic solvent and is easily to be batch produced. The thickness of the film is controllable and uniform. CaSiO3-CaAlg composite hydrogel films are expected to be used in tissue engineering and medical dressings.
Calcium silicate-calcium alginate (CaSiO3-CaAlg) composite hydrogel plate films were prepared by calcium ion cross-linking the mixture of calcium silicate and sodium alginate, and their morphologies were observed. The CaSiO3-CaAlg film was characterized by FTIR, TG and XRD. The mechanical tensile properties of CaSiO3-CaAlg composite hydrogel films with different contents of CaSiO3 on the CaAlg were investigated under wet condition. The results show that the CaSiO3 and CaAlg have good compatibility and the addition of CaSiO3 can improve the thermal performance of CaAlg. With the increase of calcium silicate in CaSiO3-CaAlg composite hydrogel membrane, the limited stress first increases, and then decreases. The preparation of CaSiO3-CaAlg composite film is simple, without using any organic solvent and is easily to be batch produced. The thickness of the film is controllable and uniform. CaSiO3-CaAlg composite hydrogel films are expected to be used in tissue engineering and medical dressings.
2017, 34(11): 2407-2413.
doi: 10.13801/j.cnki.fhclxb.20170829.002
Abstract:
Glass fiber reinforced epoxy resin(GF/EP) is used as support material for high energy physics and nuclear physics experiments due to its excellent thermal insulation and mechanical performance. High-energy physics and nuclear physics experiments produce large amounts of γ and neutron irradiation to the support material, while requiring GF/EP maintaining thermal stability as the support material. In this paper, the thermal properties including thermal expansion, thermal conductivity and thermal degradation of GF/EP under the γ irradiation of 20 kGy, 100 kGy and 200 kGy dosages were studied. The microstructure of GF/EP was observed before and after irradiation. The obtained results show that after irradiation, the microstructure of GF/EP changes, the matrix resin is fragmented, and the linear expansion range is narrowed with coefficient decreasing slightly. The thermal conductivity declines and the downward rate decreases with the increase of irradiation dosage, the thermal decomposition temperature is kept constant with the fastest thermal decomposition temperature droping slightly, the irradiation cross-linking and the irradiation degradation reaction occur simultaneously during the γ irradiation process, the overall thermal performance is stable with good stability within operating temperature range.
Glass fiber reinforced epoxy resin(GF/EP) is used as support material for high energy physics and nuclear physics experiments due to its excellent thermal insulation and mechanical performance. High-energy physics and nuclear physics experiments produce large amounts of γ and neutron irradiation to the support material, while requiring GF/EP maintaining thermal stability as the support material. In this paper, the thermal properties including thermal expansion, thermal conductivity and thermal degradation of GF/EP under the γ irradiation of 20 kGy, 100 kGy and 200 kGy dosages were studied. The microstructure of GF/EP was observed before and after irradiation. The obtained results show that after irradiation, the microstructure of GF/EP changes, the matrix resin is fragmented, and the linear expansion range is narrowed with coefficient decreasing slightly. The thermal conductivity declines and the downward rate decreases with the increase of irradiation dosage, the thermal decomposition temperature is kept constant with the fastest thermal decomposition temperature droping slightly, the irradiation cross-linking and the irradiation degradation reaction occur simultaneously during the γ irradiation process, the overall thermal performance is stable with good stability within operating temperature range.
2017, 34(11): 2414-2420.
doi: 10.13801/j.cnki.fhclxb.20170113.001
Abstract:
The surface of wood powder/polyethylene (WP/PE) composites was treated by a combined treatment of sanding then coating with a silane coupling agent and plasma discharge to improve its adhesion properties. To explore the durability of adhesive joint in hot and humid environment, the bonding strength tests and the analysis of FTIR and XPS were used to study the effect of combination treatment on the surface properties changes of WP/PE under boiling environment. The results show that, there are oxygen polar groups generated on the surface of WP/PE after combination treatment, and the chemical bonds between silane coupling agent and composite surface are formed, which improves the bonding performances tremendously. There is no new chemical group generated on the surface of WP/PE with the increase of boiling time, but the chemical environment for the element on the surface changes. The change on surface properties of WP/PE under hot and humid environment will affect the durability of adhesive joint directly. The change degree of surface properties for WP/PE is retarded by combination treatment, and the bonding properties are improved consequently, especially for the water resistance of adhesive joint.
The surface of wood powder/polyethylene (WP/PE) composites was treated by a combined treatment of sanding then coating with a silane coupling agent and plasma discharge to improve its adhesion properties. To explore the durability of adhesive joint in hot and humid environment, the bonding strength tests and the analysis of FTIR and XPS were used to study the effect of combination treatment on the surface properties changes of WP/PE under boiling environment. The results show that, there are oxygen polar groups generated on the surface of WP/PE after combination treatment, and the chemical bonds between silane coupling agent and composite surface are formed, which improves the bonding performances tremendously. There is no new chemical group generated on the surface of WP/PE with the increase of boiling time, but the chemical environment for the element on the surface changes. The change on surface properties of WP/PE under hot and humid environment will affect the durability of adhesive joint directly. The change degree of surface properties for WP/PE is retarded by combination treatment, and the bonding properties are improved consequently, especially for the water resistance of adhesive joint.
2017, 34(11): 2421-2427.
doi: 10.13801/j.cnki.fhclxb.20170222.006
Abstract:
The relationship between the thermal degradation process and the kinetic model of the modified coating was studied by using the grafted epoxy resin modified by nano-SiO2 dioxide. In order to observe its structure and understand its working temperature, the effect of nano-filler with different contents on the thermal stability of epoxy resin was tested by using KH550 modified nano-filler. The thermal characteristic temperature during thermal degradation was analyzed by TGA and DTA, and the kinetic parameters and the model fitting methods were determined. The obtained kinetic parameters were used to model the degradation process. The results show that the obtained kinetic triad is used in the degradation model of nano-SiO2/EP composites. It shows how much temperature affects the degradation time and degradation rate. The life span of the epoxy resin and the working temperature range of the nano-SiO2/EP composite are found.
The relationship between the thermal degradation process and the kinetic model of the modified coating was studied by using the grafted epoxy resin modified by nano-SiO2 dioxide. In order to observe its structure and understand its working temperature, the effect of nano-filler with different contents on the thermal stability of epoxy resin was tested by using KH550 modified nano-filler. The thermal characteristic temperature during thermal degradation was analyzed by TGA and DTA, and the kinetic parameters and the model fitting methods were determined. The obtained kinetic parameters were used to model the degradation process. The results show that the obtained kinetic triad is used in the degradation model of nano-SiO2/EP composites. It shows how much temperature affects the degradation time and degradation rate. The life span of the epoxy resin and the working temperature range of the nano-SiO2/EP composite are found.
2017, 34(11): 2428-2436.
doi: 10.13801/j.cnki.fhclxb.20170112.001
Abstract:
The carbon nanotubes (CNTs) were grown on to the surface of carbon fibers (CF) by chemical vapor deposition (CVD) method, the CF-CNTs and CF-CNTs/epoxy (EP) composites were obtained. Effects of different CVD technological parameters on the CF-CNTs multi-scale reinforcement were researched by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscope (HRTEM) methods and so on. Mechanical properties of CF-CNTs/EP composites with different CVD time were also studied. The results show that the CF-CNTs multi-scale reinforcement with the best performance can be obtained when the deposition temperature is 500℃, the deposition time is 10 min, and the corresponding reaction pressure is controlled about 0.02 MPa. The wettability of the CF-CNTs multi-scale reinforcement to EP is significantly higher than that of CF without CNTs. The interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) can be improved by 90.6% and 24.4%, respectively. At the same time, compared to the twisted CF in preparation process of EP composites, the ILSS of non-twisted CF composites can be increased by 11.3%.
The carbon nanotubes (CNTs) were grown on to the surface of carbon fibers (CF) by chemical vapor deposition (CVD) method, the CF-CNTs and CF-CNTs/epoxy (EP) composites were obtained. Effects of different CVD technological parameters on the CF-CNTs multi-scale reinforcement were researched by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscope (HRTEM) methods and so on. Mechanical properties of CF-CNTs/EP composites with different CVD time were also studied. The results show that the CF-CNTs multi-scale reinforcement with the best performance can be obtained when the deposition temperature is 500℃, the deposition time is 10 min, and the corresponding reaction pressure is controlled about 0.02 MPa. The wettability of the CF-CNTs multi-scale reinforcement to EP is significantly higher than that of CF without CNTs. The interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) can be improved by 90.6% and 24.4%, respectively. At the same time, compared to the twisted CF in preparation process of EP composites, the ILSS of non-twisted CF composites can be increased by 11.3%.
2017, 34(11): 2437-2445.
doi: 10.13801/j.cnki.fhclxb.20170224.001
Abstract:
Unidirectional carbon fiber reinforced epoxy (CFs/EP) laminate was prepared by vacuum bag molding process. By the combination of high-low temperature test box and universal testing machine, and rational use of low temperature adhesive and low temperature extensometer, cryogenic (liquid oxygen temperature, -183℃) tensile and flexural tests were conducted. During the cooling process, the stress and strain were set to zero timely. According to the microscopic and macroscopic characteristics of samples, the cryogenic mechanical properties change mechanisms of unidirectional CFs/EP laminate were revealed. The results show that, compared with the mechanical properties at room temperature, the cryogenic tensile strength of unidirectional CFs/EP laminates decreases about 9.5%, while the tensile modulus increases by about 6.2%. It is mainly due to that the resin shrinkage between carbon fibers and resin forms a strong interface at low temperature. The "split" failure mode forms in the cryogenic tensile specimen, which means that not every fiber of unidirectional CFs/EP laminate develop its full strength, and leads to the tensile strength decreasing. While the low temperature limits resin molecular chain movement, which results in the tensile modulus of unidirectional CFs/EP laminates increasing. The cryogenic flexural strength and flexural modulus of CFs/EP laminates are increased to about 54.75% and 11.64%, respectively. It is because the bending failure mode of unidirectional CFs/EP laminates at room temperature and low temperature both are delamination shear failure. The cryogenic strong interface of unidirectional CFs/EP laminates improves interlamination shear resistance and makes the cryogenic flexural properties of unidirectional CFs/EP laminates improved.
Unidirectional carbon fiber reinforced epoxy (CFs/EP) laminate was prepared by vacuum bag molding process. By the combination of high-low temperature test box and universal testing machine, and rational use of low temperature adhesive and low temperature extensometer, cryogenic (liquid oxygen temperature, -183℃) tensile and flexural tests were conducted. During the cooling process, the stress and strain were set to zero timely. According to the microscopic and macroscopic characteristics of samples, the cryogenic mechanical properties change mechanisms of unidirectional CFs/EP laminate were revealed. The results show that, compared with the mechanical properties at room temperature, the cryogenic tensile strength of unidirectional CFs/EP laminates decreases about 9.5%, while the tensile modulus increases by about 6.2%. It is mainly due to that the resin shrinkage between carbon fibers and resin forms a strong interface at low temperature. The "split" failure mode forms in the cryogenic tensile specimen, which means that not every fiber of unidirectional CFs/EP laminate develop its full strength, and leads to the tensile strength decreasing. While the low temperature limits resin molecular chain movement, which results in the tensile modulus of unidirectional CFs/EP laminates increasing. The cryogenic flexural strength and flexural modulus of CFs/EP laminates are increased to about 54.75% and 11.64%, respectively. It is because the bending failure mode of unidirectional CFs/EP laminates at room temperature and low temperature both are delamination shear failure. The cryogenic strong interface of unidirectional CFs/EP laminates improves interlamination shear resistance and makes the cryogenic flexural properties of unidirectional CFs/EP laminates improved.
2017, 34(11): 2446-2454.
doi: 10.13801/j.cnki.fhclxb.20170117.001
Abstract:
In order to effectively simulate the effective time-dependent and pseudoelastic response of shape memory alloy reinforced polymer matrix composites (SMA/PMCs), an incremental micromechanical model was constructed based on the variational asymptotic theory framework. Firstly, the incremental constitutive equations of polymer and shape memory alloys were derived, and a unified constitutive equation was established. Based on the unified constitutive equation, the variational expression of energy functional was derived. The incremental process associated with the instantaneous effective tangential matrix was constructed, solved and numerical implemented by the finite element method. The numerical examples show that the constructed model can be used to simulate the time-dependent pseudoelastic response of SMA/PMCs under different loading and temperature change rate, and accurately capture the rate-dependent and hysteretic behavior introduced by the viscoelastic behavior of polymer matrix.
In order to effectively simulate the effective time-dependent and pseudoelastic response of shape memory alloy reinforced polymer matrix composites (SMA/PMCs), an incremental micromechanical model was constructed based on the variational asymptotic theory framework. Firstly, the incremental constitutive equations of polymer and shape memory alloys were derived, and a unified constitutive equation was established. Based on the unified constitutive equation, the variational expression of energy functional was derived. The incremental process associated with the instantaneous effective tangential matrix was constructed, solved and numerical implemented by the finite element method. The numerical examples show that the constructed model can be used to simulate the time-dependent pseudoelastic response of SMA/PMCs under different loading and temperature change rate, and accurately capture the rate-dependent and hysteretic behavior introduced by the viscoelastic behavior of polymer matrix.
2017, 34(11): 2455-2462.
doi: 10.13801/j.cnki.fhclxb.20170308.002
Abstract:
The thermal mechanical analyzer and micro-indentation test system were used to characterize the mechanical properties of isotropic conductive adhesive (ICA) with different silver contents. Based on numerical simulation, the thermal mismatch stress of cured ICA in flip chip packaging was analyzed. The results show that the glass transition temperature of cured ICA with high silver content is relatively higher and the thermal expansion coefficient is lower than those of cured ICA with low silver content. The elastic modulus and hardness of the cured ICA are higher in the glassy state than those in the high-elastic state, and the stiffness and strength are relatively larger for cured ICA with high silver content. On the whole, with the increasing temperature the maximum of thermal stress component increases, then declines rapidly, and decreases slowly, showing a "tadpole shaped" or "semi-tadpole shaped". In the glassy state, the conductive adhesive in flip chip packaging exhibits elasticity.
The thermal mechanical analyzer and micro-indentation test system were used to characterize the mechanical properties of isotropic conductive adhesive (ICA) with different silver contents. Based on numerical simulation, the thermal mismatch stress of cured ICA in flip chip packaging was analyzed. The results show that the glass transition temperature of cured ICA with high silver content is relatively higher and the thermal expansion coefficient is lower than those of cured ICA with low silver content. The elastic modulus and hardness of the cured ICA are higher in the glassy state than those in the high-elastic state, and the stiffness and strength are relatively larger for cured ICA with high silver content. On the whole, with the increasing temperature the maximum of thermal stress component increases, then declines rapidly, and decreases slowly, showing a "tadpole shaped" or "semi-tadpole shaped". In the glassy state, the conductive adhesive in flip chip packaging exhibits elasticity.
2017, 34(11): 2463-2472.
doi: 10.13801/j.cnki.fhclxb.20170307.001
Abstract:
Based on the analysis on the change of the fiber bundle's cross-section and its constitutive model, compression model of two-layer fabrics was established with different nesting. The model associated fabric thickness with compression load, fabric structure and layer shifting could be used to describe the compressive behavior under any nested state. On this basis, the multilayer fabric compression model was further established. Through the numerical solution of the above model, the compressive response of different layers was predicted. The main conclusions are as follows:The average thickness decreases with the increase of shifting ratio at a given pressure. The distribution of average thickness per layer takes the shape close to a typical distribution at a given pressure and becomes narrow with the increase of the number of layers. When the number of layers is more than 10, the compaction properties of multi-layer fabrics can be described by the mathematical expectation of the thickness of inner layer as a function of external load. The model is in well accordance with the experimental data. The feasibility of the model is verified.
Based on the analysis on the change of the fiber bundle's cross-section and its constitutive model, compression model of two-layer fabrics was established with different nesting. The model associated fabric thickness with compression load, fabric structure and layer shifting could be used to describe the compressive behavior under any nested state. On this basis, the multilayer fabric compression model was further established. Through the numerical solution of the above model, the compressive response of different layers was predicted. The main conclusions are as follows:The average thickness decreases with the increase of shifting ratio at a given pressure. The distribution of average thickness per layer takes the shape close to a typical distribution at a given pressure and becomes narrow with the increase of the number of layers. When the number of layers is more than 10, the compaction properties of multi-layer fabrics can be described by the mathematical expectation of the thickness of inner layer as a function of external load. The model is in well accordance with the experimental data. The feasibility of the model is verified.
2017, 34(11): 2473-2478.
doi: 10.13801/j.cnki.fhclxb.20170307.003
Abstract:
In order to understand the mechanical property of the fiber reinforced epexy resin composite with ply splice structure and get strong ply splice structures, the tensile properties of three kinds of unidirectional CF/EP with ply splice structures were tested. The tensile specimens were monitored during the loading process to analyze the fracture process, and finite element method (FEM) was used to study the character of the stress distributions when the ply splice structures were under a tensile load. All the CF/EP materials were prepared through vacuum assisted resin transfer molding (VARTM) process. The results show that, inducing ply splices into CF/EP materials, the tensile strength decreases evidently. Due to the ply splice, stress concentrations occur, and the initial fracture happens in the ply splice position, leading to the final fracture on the interfaces between different plies. The interlaminar shear stress and the tensile stress in the through-thickness direction near the ply splice position are the key factors leading to the initial failure. In order to get stronger ply splice structures, symmetric structures should be adopted.
In order to understand the mechanical property of the fiber reinforced epexy resin composite with ply splice structure and get strong ply splice structures, the tensile properties of three kinds of unidirectional CF/EP with ply splice structures were tested. The tensile specimens were monitored during the loading process to analyze the fracture process, and finite element method (FEM) was used to study the character of the stress distributions when the ply splice structures were under a tensile load. All the CF/EP materials were prepared through vacuum assisted resin transfer molding (VARTM) process. The results show that, inducing ply splices into CF/EP materials, the tensile strength decreases evidently. Due to the ply splice, stress concentrations occur, and the initial fracture happens in the ply splice position, leading to the final fracture on the interfaces between different plies. The interlaminar shear stress and the tensile stress in the through-thickness direction near the ply splice position are the key factors leading to the initial failure. In order to get stronger ply splice structures, symmetric structures should be adopted.
2017, 34(11): 2479-2486.
doi: 10.13801/j.cnki.fhclxb.20170626.001
Abstract:
In order to predict the post-buckling loading capability of omega stiffened composite panel accurately, the failure mechanism and failure load of omega stiffened composite panel with tapered stringers under compressive load were investigated. Firstly, the failure process of stiffened panel with tapered stringers was explored based on specimen experiment, and a nonlinear progressive damage model with the failure of adhesive interface and composite laminate was established to study the damage initiation and failure process in detail. Then, the method for the skin/flange interface enhanced by cladding layer was proposed, and the influence of the cladding layer on the failure mode and carrying capability has been explored by numerical simulation and test. The results show that the buckling load and post-buckling loading of the panel reinforced by cladding layer increase significantly. Moreover, the FE results for loading capability and the failure mode coincide with the test results.
In order to predict the post-buckling loading capability of omega stiffened composite panel accurately, the failure mechanism and failure load of omega stiffened composite panel with tapered stringers under compressive load were investigated. Firstly, the failure process of stiffened panel with tapered stringers was explored based on specimen experiment, and a nonlinear progressive damage model with the failure of adhesive interface and composite laminate was established to study the damage initiation and failure process in detail. Then, the method for the skin/flange interface enhanced by cladding layer was proposed, and the influence of the cladding layer on the failure mode and carrying capability has been explored by numerical simulation and test. The results show that the buckling load and post-buckling loading of the panel reinforced by cladding layer increase significantly. Moreover, the FE results for loading capability and the failure mode coincide with the test results.
2017, 34(11): 2487-2493.
doi: 10.13801/j.cnki.fhclxb.20170302.001
Abstract:
To investigate the transverse compression deformation mechanism of high performance fiber bundles, by mean of ANSYS parametric design language (APDL) with commercial finite element codes ANSYS, a 3D statistical generation-growth numerical model was proposed to generate a micro morphology of continuous fiber bundle. Both the random distribution and the misalignment of fiber in the generation were considered. Penetration of any two fibers was not allowed physically which was also reflected in the protocol. On the base of the generation-growth numerical model, the transverse compression deformation of high performance fiber bundles was simulated. The numerical simulation is not only consistent with the non-linear compression loading curves of experiments, but also allows the identification of the power laws to represent the evolutions of the compressive load and the fiber volume fraction.
To investigate the transverse compression deformation mechanism of high performance fiber bundles, by mean of ANSYS parametric design language (APDL) with commercial finite element codes ANSYS, a 3D statistical generation-growth numerical model was proposed to generate a micro morphology of continuous fiber bundle. Both the random distribution and the misalignment of fiber in the generation were considered. Penetration of any two fibers was not allowed physically which was also reflected in the protocol. On the base of the generation-growth numerical model, the transverse compression deformation of high performance fiber bundles was simulated. The numerical simulation is not only consistent with the non-linear compression loading curves of experiments, but also allows the identification of the power laws to represent the evolutions of the compressive load and the fiber volume fraction.
2017, 34(11): 2494-2499.
doi: 10.13801/j.cnki.fhclxb.20170112.004
Abstract:
Carbon encapsulated NiO(NiO@C) nano particles were successfully prepared by DC arc discharging plasma technology. The product is characterized by HRTEM, XRD, X-ray energy dispersive spectrometry (XEDS), Raman spectroscopy and low-temperature N2 adsorption desorption to determine the morphology, crystal structure, particle size, specific area and pore structure. The experimental results indicate that the NiO@C nano-particles prepared by DC arc plasma technology possess typical core shell structure, the core of the particles is NiO with face centered cubic structure, and the outer shell is disordered carbon layer. The particle morphology exhibits cube structure with uniform particle size and good dispersion. The particle size distribution is in the range of 30-70 nm, the average particle size is 50 nm, and the thickness of the carbon shell is about 5 nm. The BET specific surface area of the carbon encapsulated NiO nano particles is 28 m2/g, and the equivalent particle size is 46 nm, which is consistent with the results measured by HRTEM and XRD. Raman spectrum shows that the degree of graphite in the sample is low, and the red shift phenomenon occurs.
Carbon encapsulated NiO(NiO@C) nano particles were successfully prepared by DC arc discharging plasma technology. The product is characterized by HRTEM, XRD, X-ray energy dispersive spectrometry (XEDS), Raman spectroscopy and low-temperature N2 adsorption desorption to determine the morphology, crystal structure, particle size, specific area and pore structure. The experimental results indicate that the NiO@C nano-particles prepared by DC arc plasma technology possess typical core shell structure, the core of the particles is NiO with face centered cubic structure, and the outer shell is disordered carbon layer. The particle morphology exhibits cube structure with uniform particle size and good dispersion. The particle size distribution is in the range of 30-70 nm, the average particle size is 50 nm, and the thickness of the carbon shell is about 5 nm. The BET specific surface area of the carbon encapsulated NiO nano particles is 28 m2/g, and the equivalent particle size is 46 nm, which is consistent with the results measured by HRTEM and XRD. Raman spectrum shows that the degree of graphite in the sample is low, and the red shift phenomenon occurs.
2017, 34(11): 2500-2508.
doi: 10.13801/j.cnki.fhclxb.20170303.002
Abstract:
A kind of Fe-based ceramic coatings with ZrB2 and ZrC as multi scale strengthening phases on the surface of Q235 steel were fabricated by plasma cladding using Fe, Zr, and B4C powder mixture as precursor. The phase composition, microstructure, microhardness and the wear resistance comparative test of ZrB2-ZrC/Fe coating and Q235 steel were investigated. The microstructure evolution, the formation of the phase and the wear mechanism were discussed. The results show that ZrB2-ZrC/Fe coatings are composed of ZrB2, ZrC, α-Fe, Fe3C and Fe2B phases. ZrB2 phase presents acicular, clubbed and petal forms. ZrC phase is irregular polygon shape. With the increasing of (Zr+B4C) raw powder, the contents of ZrB2 and ZrC are increasing, the size of ZrB2 and ZrC become large. The plasma clad ZrB2-ZrC/Fe composite coating is closely and metallurgically bonded to the Q235 steel substrate. Compared with Q235 steel substrate, the wear resistance of the coating is improved significantly, up to 5.45 times than that of the substrate. The main wear mechanism of ZrB2-ZrC/Fe composite coating is abrasive wear, the main fracture mode of the composite coating is transgranular fracture.
A kind of Fe-based ceramic coatings with ZrB2 and ZrC as multi scale strengthening phases on the surface of Q235 steel were fabricated by plasma cladding using Fe, Zr, and B4C powder mixture as precursor. The phase composition, microstructure, microhardness and the wear resistance comparative test of ZrB2-ZrC/Fe coating and Q235 steel were investigated. The microstructure evolution, the formation of the phase and the wear mechanism were discussed. The results show that ZrB2-ZrC/Fe coatings are composed of ZrB2, ZrC, α-Fe, Fe3C and Fe2B phases. ZrB2 phase presents acicular, clubbed and petal forms. ZrC phase is irregular polygon shape. With the increasing of (Zr+B4C) raw powder, the contents of ZrB2 and ZrC are increasing, the size of ZrB2 and ZrC become large. The plasma clad ZrB2-ZrC/Fe composite coating is closely and metallurgically bonded to the Q235 steel substrate. Compared with Q235 steel substrate, the wear resistance of the coating is improved significantly, up to 5.45 times than that of the substrate. The main wear mechanism of ZrB2-ZrC/Fe composite coating is abrasive wear, the main fracture mode of the composite coating is transgranular fracture.
2017, 34(11): 2509-2515.
doi: 10.13801/j.cnki.fhclxb.20170321.004
Abstract:
The stability, magnetic and electronic properties of transition metal (TM) Fe or Cr monoatomic chain encapsulated into (6, 6) Cu nanotube (Fe@CuNT or Cr@CuNT) were systematically investigated by the first-principles calculations based on density-functional theory. The results indicate that the binding energies per TM atom of the Fe@CuNT and Cr@CuNT hybrid structures are remarkably higher than those of corresponding freestanding TM chains, indicating the TM chains are significantly stabilized by the Cu nanotube coating. The formed bonds between outer Cu and inner TM atoms show metallic bonding character. The magnetic ground states of Fe@CuNT and Cr@CuNT hybrid structures are ferromagnetic and antiferromagnetic states, respectively. The spin and orbital magnetic moments of inner Fe and Cr atoms of Fe@CuNT and Cr@CuNT hybrid structures were calculated. The magnetocrystalline anisotropy energies (MAE) of Fe@CuNT and Cr@CuNT hybrid structures are all significantly enhanced compared to those of corresponding freestanding TM chains, suggesting that Fe@CuNT and Cr@CuNT hybrid structures can be used in ultrahigh density magnetic storage. Furthermore, the easy magnetization direction switches from that along the chain direction in freestanding Fe chain to that perpendicular to the chain direction in Fe@CuNT hybrid structure. The large spin polarization at the Fermi level also makes the Fe@CuNT hybrid structure interesting as a potential candidate for spin-dependent transport applications.
The stability, magnetic and electronic properties of transition metal (TM) Fe or Cr monoatomic chain encapsulated into (6, 6) Cu nanotube (Fe@CuNT or Cr@CuNT) were systematically investigated by the first-principles calculations based on density-functional theory. The results indicate that the binding energies per TM atom of the Fe@CuNT and Cr@CuNT hybrid structures are remarkably higher than those of corresponding freestanding TM chains, indicating the TM chains are significantly stabilized by the Cu nanotube coating. The formed bonds between outer Cu and inner TM atoms show metallic bonding character. The magnetic ground states of Fe@CuNT and Cr@CuNT hybrid structures are ferromagnetic and antiferromagnetic states, respectively. The spin and orbital magnetic moments of inner Fe and Cr atoms of Fe@CuNT and Cr@CuNT hybrid structures were calculated. The magnetocrystalline anisotropy energies (MAE) of Fe@CuNT and Cr@CuNT hybrid structures are all significantly enhanced compared to those of corresponding freestanding TM chains, suggesting that Fe@CuNT and Cr@CuNT hybrid structures can be used in ultrahigh density magnetic storage. Furthermore, the easy magnetization direction switches from that along the chain direction in freestanding Fe chain to that perpendicular to the chain direction in Fe@CuNT hybrid structure. The large spin polarization at the Fermi level also makes the Fe@CuNT hybrid structure interesting as a potential candidate for spin-dependent transport applications.
2017, 34(11): 2516-2522.
doi: 10.13801/j.cnki.fhclxb.20170216.002
Abstract:
In order to enhance the osseointegration of Ti implant, chemical conversion technology was used to prepare a calcium phosphate (CaP) coating on Ti. The alkali treatment was conducted to rise a secondary coating on the primary coated Ti. The phase composition, microstructure and corrosion resistance of the CaP coated Ti (Ti-CaP) samples were investigated using the XRD, field emission SEM and electrochemical measurements, respectively. The cytocompatibility was evaluated by the cell attachment, proliferation and alkaline phosphatase (ALP) activity of MC3T3-E1 cells. The results show that the primary coating formed on Ti is mainly composed of brushite (CaHPO4·2H2O) with a blocky structure. After alkali treatment, the brushite crystals are partly transformed to hydroxyapatite (HA) crystals with a coarser surface and some newborn crystals. The electrochemical measurements reveal that the corrosion resistance of the HA coated Ti is better than that of the brushite coated Ti. In vitro cell tests demonstrate that the surface of the coated Ti samples exhibit better cytocompatibility than that of pure Ti.
In order to enhance the osseointegration of Ti implant, chemical conversion technology was used to prepare a calcium phosphate (CaP) coating on Ti. The alkali treatment was conducted to rise a secondary coating on the primary coated Ti. The phase composition, microstructure and corrosion resistance of the CaP coated Ti (Ti-CaP) samples were investigated using the XRD, field emission SEM and electrochemical measurements, respectively. The cytocompatibility was evaluated by the cell attachment, proliferation and alkaline phosphatase (ALP) activity of MC3T3-E1 cells. The results show that the primary coating formed on Ti is mainly composed of brushite (CaHPO4·2H2O) with a blocky structure. After alkali treatment, the brushite crystals are partly transformed to hydroxyapatite (HA) crystals with a coarser surface and some newborn crystals. The electrochemical measurements reveal that the corrosion resistance of the HA coated Ti is better than that of the brushite coated Ti. In vitro cell tests demonstrate that the surface of the coated Ti samples exhibit better cytocompatibility than that of pure Ti.
2017, 34(11): 2523-2529.
doi: 10.13801/j.cnki.fhclxb.20170401.002
Abstract:
TiC layer was coated on the surface of the nature graphite flake (GF) by the molten salt method, and then GF/Cu composites were fabricated by vacuum hot-press sintering with TiC coated GF and Cu powder. The effects of volume fraction of GF and TiC coating on the thermal conductivity and flexural strength of the composites were investigated. A series of analysis results show that with the decrease of volume fraction of GF and the formation of TiC layer, the thermal conductivity of TiC-GF/Cu composites decreases in the direction of the parallel graphite layer while the trend of flexural strength is increased.When the volume fraction of GF is 70% of TiC-GF/Cu composites, the thermal conductivity of TiC-GF/Cu composites along the plane parallel to the graphite laminate decreases from 676 W/(m·K) to 526 W/(m·K), and the flexural strength of TiC coated GF/Cu composites is significantly enhanced from 52 MPa to 103 MPa.Meanwhile, microstructure features of TiC-GF/Cu composites further illustrate that TiC coated on the surface of GF plays an important role on the fracture model of GF/Cu composites.
TiC layer was coated on the surface of the nature graphite flake (GF) by the molten salt method, and then GF/Cu composites were fabricated by vacuum hot-press sintering with TiC coated GF and Cu powder. The effects of volume fraction of GF and TiC coating on the thermal conductivity and flexural strength of the composites were investigated. A series of analysis results show that with the decrease of volume fraction of GF and the formation of TiC layer, the thermal conductivity of TiC-GF/Cu composites decreases in the direction of the parallel graphite layer while the trend of flexural strength is increased.When the volume fraction of GF is 70% of TiC-GF/Cu composites, the thermal conductivity of TiC-GF/Cu composites along the plane parallel to the graphite laminate decreases from 676 W/(m·K) to 526 W/(m·K), and the flexural strength of TiC coated GF/Cu composites is significantly enhanced from 52 MPa to 103 MPa.Meanwhile, microstructure features of TiC-GF/Cu composites further illustrate that TiC coated on the surface of GF plays an important role on the fracture model of GF/Cu composites.
2017, 34(11): 2530-2536.
doi: 10.13801/j.cnki.fhclxb.20170302.005
Abstract:
nano SiC fiber modified chopped carbon fiber (nano SiCf-Cfd) was prepred by catalytic chemical vapor deposition using Methyltrichlorosilane (MTS) as the precursor. Afterwards, nano SiCf-Cfd/Si3N4 and Cfd/Si3N4 composites were manufactured by two-steps process, gelcasting and atmospheric sintering. The influence of nano SiCf-Cfd and Cfd on dielectric response and microwave absorption properties within X-band(8.2-12.4 GHz) was studied by using network analyzer. The results show that the complex dielectric constant and dielectric loss tangent (tan δ)of two composites increase with the added amount of fiber. At the same fiber content, the real part of the dielectric constant of nano SiCf-Cfd/Si3N4 composite is lower than that of Cfd/Si3N4 composites, but tan δ increases. Additionally, the results of calculated reflectivity show that nano SiCf-Cfd/Si3N4 composites have strong microwave absorption. When the content of nano SiCf-Cfd is 2wt% and the thickness is 2.5 mm, the maximum absorption peak can reach -14.95 dB. Moreover, the bandwidth of reflectivity (less than -5 dB) is up to 3.5 GHz. Therefore, nano SiCf modification can effectively improve the microwave absorption property of Cfd/Si3N4 composites.
nano SiC fiber modified chopped carbon fiber (nano SiCf-Cfd) was prepred by catalytic chemical vapor deposition using Methyltrichlorosilane (MTS) as the precursor. Afterwards, nano SiCf-Cfd/Si3N4 and Cfd/Si3N4 composites were manufactured by two-steps process, gelcasting and atmospheric sintering. The influence of nano SiCf-Cfd and Cfd on dielectric response and microwave absorption properties within X-band(8.2-12.4 GHz) was studied by using network analyzer. The results show that the complex dielectric constant and dielectric loss tangent (tan δ)of two composites increase with the added amount of fiber. At the same fiber content, the real part of the dielectric constant of nano SiCf-Cfd/Si3N4 composite is lower than that of Cfd/Si3N4 composites, but tan δ increases. Additionally, the results of calculated reflectivity show that nano SiCf-Cfd/Si3N4 composites have strong microwave absorption. When the content of nano SiCf-Cfd is 2wt% and the thickness is 2.5 mm, the maximum absorption peak can reach -14.95 dB. Moreover, the bandwidth of reflectivity (less than -5 dB) is up to 3.5 GHz. Therefore, nano SiCf modification can effectively improve the microwave absorption property of Cfd/Si3N4 composites.
2017, 34(11): 2537-2543.
doi: 10.13801/j.cnki.fhclxb.20170112.006
Abstract:
The structural stability of Al2TiO5ss/3Al2O3·2SiO2ss composite based on middle-low grade bauxite calcined at 1 600℃ and held subsequently at 1 200℃ for 12 h was studied by XRD, SEM and energy dispersive spectroscope (EDS). The results show that after middle-low grade bauxite being calcined at 1 600℃, its crystal phase composition consists of 3Al2O3·2SiO2ss, Al2TiO5ss and a little cristobalite, in which Fe3+/Ti4+ cations exsit in crystalline phases (3Al2O3·2SiO2ss and Al2TiO5ss) and amorphous phase (silicate) in different forms. Al2TiO5ss is separated and huddled by 3Al2O3·2SiO2ss containing Fe3+/Ti4+ cations, restraining its decomposition; in addition, both 3Al2O3·2SiO2ss and Al2TiO5ss build compact skeleton structure of Al2TiO5ss/3Al2O3·2SiO2ss synthesis system based on middle-low grade bauxite due to their near element composition, which avoids appearance of silicate phases with low melting point and further endows good structural stability.
The structural stability of Al2TiO5ss/3Al2O3·2SiO2ss composite based on middle-low grade bauxite calcined at 1 600℃ and held subsequently at 1 200℃ for 12 h was studied by XRD, SEM and energy dispersive spectroscope (EDS). The results show that after middle-low grade bauxite being calcined at 1 600℃, its crystal phase composition consists of 3Al2O3·2SiO2ss, Al2TiO5ss and a little cristobalite, in which Fe3+/Ti4+ cations exsit in crystalline phases (3Al2O3·2SiO2ss and Al2TiO5ss) and amorphous phase (silicate) in different forms. Al2TiO5ss is separated and huddled by 3Al2O3·2SiO2ss containing Fe3+/Ti4+ cations, restraining its decomposition; in addition, both 3Al2O3·2SiO2ss and Al2TiO5ss build compact skeleton structure of Al2TiO5ss/3Al2O3·2SiO2ss synthesis system based on middle-low grade bauxite due to their near element composition, which avoids appearance of silicate phases with low melting point and further endows good structural stability.
2017, 34(11): 2544-2549.
doi: 10.13801/j.cnki.fhclxb.20170220.003
Abstract:
Graphene nanosheets(GNSs)/SiC-Cu and carbon nano-tubes(CNTs)/SiC-Cu reinforcements were prepared on the surface of electroless Cu (ECu) plating and photodeposition Cu (PCu) plating SiC-Cu particles respectively by chemical vapor deposition (CVD). The effects of temperature and holding time during the preparation on the layers and the quality of GNSs and CNTs were studied by Raman spectroscopy and SEM. The results show that multilayer GNSs and CNTs are successfully prepared on both the surface of ECu plating and PCu plating SiC-Cu particles by CVD. The GNSs prepared at 1 000℃ for 20 min on ECu plating SiC-Cu particles are successfully obtained with good quality and less layer (almost monolayer). The CNTs in the state of interlaced distribution are found between the copper atoms by SEM, whose diameter ranges 10-45 nm.
Graphene nanosheets(GNSs)/SiC-Cu and carbon nano-tubes(CNTs)/SiC-Cu reinforcements were prepared on the surface of electroless Cu (ECu) plating and photodeposition Cu (PCu) plating SiC-Cu particles respectively by chemical vapor deposition (CVD). The effects of temperature and holding time during the preparation on the layers and the quality of GNSs and CNTs were studied by Raman spectroscopy and SEM. The results show that multilayer GNSs and CNTs are successfully prepared on both the surface of ECu plating and PCu plating SiC-Cu particles by CVD. The GNSs prepared at 1 000℃ for 20 min on ECu plating SiC-Cu particles are successfully obtained with good quality and less layer (almost monolayer). The CNTs in the state of interlaced distribution are found between the copper atoms by SEM, whose diameter ranges 10-45 nm.
2017, 34(11): 2550-2555.
doi: 10.13801/j.cnki.fhclxb.20170220.005
Abstract:
The small diameter artificial blood vessel(d=3.0 mm) of polylactide acid and collagen (Col-PLA)was prepared by electrospinning in this paper. The fiber morphology on the surface, pore size and tensile property of Col-PLA artificial blood vessel were characterized by scanning electron microscopy, pore size analyzer and tensile testing machine, respectively. The wall thickness and burst strength were also measured. The influence of spinning voltage, spinning solution mass fraction and mass ratio of PLA to Col on the structure and properties of artificial blood vessel were investigated. The results show that the fiber array is changed into regular with the increasing of the spinning voltage, and the optimal spinning voltage is between 15-20 kV. The fiber diameter and the mechanical properties of artificial blood vessel increase with the increasing of the spinning solution mass fraction, while the porosity and pore size decrease. As mass ratio of PLA to Col increase, the inner layer thickness of Col-PLA artificial blood vessel decrease and the outer layer thickness increase, which lead to the tensile strength and burst strength of the artificial blood vessel improvement. When the mass ratio of PLA to Col are 70:30 and 90:10, the mechanical properties of artificial vessel can meet the requirements.
The small diameter artificial blood vessel(d=3.0 mm) of polylactide acid and collagen (Col-PLA)was prepared by electrospinning in this paper. The fiber morphology on the surface, pore size and tensile property of Col-PLA artificial blood vessel were characterized by scanning electron microscopy, pore size analyzer and tensile testing machine, respectively. The wall thickness and burst strength were also measured. The influence of spinning voltage, spinning solution mass fraction and mass ratio of PLA to Col on the structure and properties of artificial blood vessel were investigated. The results show that the fiber array is changed into regular with the increasing of the spinning voltage, and the optimal spinning voltage is between 15-20 kV. The fiber diameter and the mechanical properties of artificial blood vessel increase with the increasing of the spinning solution mass fraction, while the porosity and pore size decrease. As mass ratio of PLA to Col increase, the inner layer thickness of Col-PLA artificial blood vessel decrease and the outer layer thickness increase, which lead to the tensile strength and burst strength of the artificial blood vessel improvement. When the mass ratio of PLA to Col are 70:30 and 90:10, the mechanical properties of artificial vessel can meet the requirements.
2017, 34(11): 2556-2561.
doi: 10.13801/j.cnki.fhclxb.20170112.003
Abstract:
With n-octadecane, methyl methacrylate and chitosan as the core material, inner shell and outside shell respectively, the double-shell phase change and humidity storage micro-capsules were made by in-situ polymerization and emulsion interfacial polymerization method. Combining the uniform design and radial basis function neural network, the effect of parameters (i.e. emulsifier amount, co-emulsifier amount, initiator amount, phacoemulsification time and mixing speed) on particle size distribution of double-shell phase change and humidity storage micro-capsules were investigated. In addition, the optimal uniform particle size distribution of double-shell phase change and humidity storage micro-capsules were tested and characterized. The results show that radial basis function(RBF) neural network has the best approximation effect when "Spread" is 0.55. To obtain optimal uniform particle size distribution for double-shell phase change and humidity storage micro-capsules, the preparation parameters are identified as follows:emulsifier amount to be 3.58wt%, co-emulsifier amount to be 0.53wt%, initiator amount to be 1.86wt%, phacoemulsification time to be 11.35 min and mixing speed to be 632 r·min-1. On the base of the above preparation parameters, d10 is 3 352.0 nm, d50 is 4 474.9 nm, d90 is 6 108.4 nm, and the measured value of d90-d10 is 2 756.4 nm. Therefore, the measured value agrees well with the predictive value (relative error is 2.69%). In the case of relative humidity between 35% and 65%, the equilibrium moisture content is obtained to be between 0.0547 g·g-1 and 0.1259 g·g-1, phase transition temperature is 28.87℃ and phase change enthalpy is 78.45 J·g-1.
With n-octadecane, methyl methacrylate and chitosan as the core material, inner shell and outside shell respectively, the double-shell phase change and humidity storage micro-capsules were made by in-situ polymerization and emulsion interfacial polymerization method. Combining the uniform design and radial basis function neural network, the effect of parameters (i.e. emulsifier amount, co-emulsifier amount, initiator amount, phacoemulsification time and mixing speed) on particle size distribution of double-shell phase change and humidity storage micro-capsules were investigated. In addition, the optimal uniform particle size distribution of double-shell phase change and humidity storage micro-capsules were tested and characterized. The results show that radial basis function(RBF) neural network has the best approximation effect when "Spread" is 0.55. To obtain optimal uniform particle size distribution for double-shell phase change and humidity storage micro-capsules, the preparation parameters are identified as follows:emulsifier amount to be 3.58wt%, co-emulsifier amount to be 0.53wt%, initiator amount to be 1.86wt%, phacoemulsification time to be 11.35 min and mixing speed to be 632 r·min-1. On the base of the above preparation parameters, d10 is 3 352.0 nm, d50 is 4 474.9 nm, d90 is 6 108.4 nm, and the measured value of d90-d10 is 2 756.4 nm. Therefore, the measured value agrees well with the predictive value (relative error is 2.69%). In the case of relative humidity between 35% and 65%, the equilibrium moisture content is obtained to be between 0.0547 g·g-1 and 0.1259 g·g-1, phase transition temperature is 28.87℃ and phase change enthalpy is 78.45 J·g-1.
2017, 34(11): 2562-2570.
doi: 10.13801/j.cnki.fhclxb.20170216.001
Abstract:
It is not very easy to directly dope Zr into the mesoporous SiO2.This is due to Zr species are generally difficult to co-condensation with siliceous species and then be co-incorporated into the framework of the SiO2 under strong acidic conditions. Therefore, a series of mesoporous Zr-SiO2 were successfully synthesized by a one-step method in the mildly acidic solutions that contain surfactant, hydrochloride acid, zinc acetate, siliceous and zirconium species. Experimental results show that all Zr-SiO2 samples synthesized with the Zr:Si molar ratio (r) equal to or less than 0.2:1 have the well-ordered mesostructures. The integrity of the mesostructure will decrease if further increase the r to 0.3 or 0.5. When the r in the initial reaction solution changes from 0.01 to 0.2, the cell parameter of the corresponding obtained material increases from 9.7 to 10.9 nm, and the wall thickness of the Zr-SiO2 sample also enlarges from 1.4 to 2.6 nm, respectively. This confirms that Zr species are incorporated into the framework of mesoporous SiO2. The morphology of the Zr-SiO2 can be controlled by the incorporation of different amounts of Zr species. The highly regular fine particles with morphologies such as wormlike, grape-like and wheat grain-like are then obtained for the Zr-SiO2 samples. The mesoporous Zr-SiO2 materials present high adsorption abilities in the removal of methylene blue dye from aqueous solutions.
It is not very easy to directly dope Zr into the mesoporous SiO2.This is due to Zr species are generally difficult to co-condensation with siliceous species and then be co-incorporated into the framework of the SiO2 under strong acidic conditions. Therefore, a series of mesoporous Zr-SiO2 were successfully synthesized by a one-step method in the mildly acidic solutions that contain surfactant, hydrochloride acid, zinc acetate, siliceous and zirconium species. Experimental results show that all Zr-SiO2 samples synthesized with the Zr:Si molar ratio (r) equal to or less than 0.2:1 have the well-ordered mesostructures. The integrity of the mesostructure will decrease if further increase the r to 0.3 or 0.5. When the r in the initial reaction solution changes from 0.01 to 0.2, the cell parameter of the corresponding obtained material increases from 9.7 to 10.9 nm, and the wall thickness of the Zr-SiO2 sample also enlarges from 1.4 to 2.6 nm, respectively. This confirms that Zr species are incorporated into the framework of mesoporous SiO2. The morphology of the Zr-SiO2 can be controlled by the incorporation of different amounts of Zr species. The highly regular fine particles with morphologies such as wormlike, grape-like and wheat grain-like are then obtained for the Zr-SiO2 samples. The mesoporous Zr-SiO2 materials present high adsorption abilities in the removal of methylene blue dye from aqueous solutions.
2017, 34(11): 2571-2579.
doi: 10.13801/j.cnki.fhclxb.20170112.007
Abstract:
The silk fibroin(SF)/sodium alginate(SA) double network composite fiber was prepared by incorporating silk fibroin cross-linked with polyethylene glycol diglycidyl ether(PEGDE) as a cross-linking agent into sodium alginate cross-linked with CaCl2 as a cross-linking agent. The apparent viscosity of spinning solution and properties of as-prepared crosslinking modified composite fiber were characterized by DV-C display viscosity meter, FTIR, Electronic single fiber strength tester, nuclear magnetic resonance temperature relaxation analyzer, SEM and XRD. The effects of cross-linking agent PEGDE content on the mechanical properties, micromorphologies, cross-linking degree, moisture absorption performance and preserve moisturizing performance of cross-linking modified SF/SA composite fiber were investigated in details.The results indicate that the apparent viscosity of spinning solution decreases first and then increases as the crosslinking agent is added; addition of appropriate amount of crosslinking agent can reduce the apparent viscosity of the spinning solution and increase the spinnability of the fiber; while it affects the breaking strength, the breaking elongation and the degree of cross linking in the opposite way. More specifically, the breaking strength and crosslinking degree both reach the maximum (2.34 cN/dtex and 55.8%, respectively), when the mass ration of crosslinking agent PEGDE and silk fibroin is 3:1. The higher the degree of crosslinking is, the more significant the trench structure on the surface of crosslinking modified SF/SA composite fiber is and the better for the compatibility of the composite fiber. In addition, hygroscopicity and moisture retention of crosslinking modified composite fiber has been improved and the moisture absorption equilibrium time is advanced.
The silk fibroin(SF)/sodium alginate(SA) double network composite fiber was prepared by incorporating silk fibroin cross-linked with polyethylene glycol diglycidyl ether(PEGDE) as a cross-linking agent into sodium alginate cross-linked with CaCl2 as a cross-linking agent. The apparent viscosity of spinning solution and properties of as-prepared crosslinking modified composite fiber were characterized by DV-C display viscosity meter, FTIR, Electronic single fiber strength tester, nuclear magnetic resonance temperature relaxation analyzer, SEM and XRD. The effects of cross-linking agent PEGDE content on the mechanical properties, micromorphologies, cross-linking degree, moisture absorption performance and preserve moisturizing performance of cross-linking modified SF/SA composite fiber were investigated in details.The results indicate that the apparent viscosity of spinning solution decreases first and then increases as the crosslinking agent is added; addition of appropriate amount of crosslinking agent can reduce the apparent viscosity of the spinning solution and increase the spinnability of the fiber; while it affects the breaking strength, the breaking elongation and the degree of cross linking in the opposite way. More specifically, the breaking strength and crosslinking degree both reach the maximum (2.34 cN/dtex and 55.8%, respectively), when the mass ration of crosslinking agent PEGDE and silk fibroin is 3:1. The higher the degree of crosslinking is, the more significant the trench structure on the surface of crosslinking modified SF/SA composite fiber is and the better for the compatibility of the composite fiber. In addition, hygroscopicity and moisture retention of crosslinking modified composite fiber has been improved and the moisture absorption equilibrium time is advanced.
2017, 34(11): 2580-2585.
doi: 10.13801/j.cnki.fhclxb.20170228.002
Abstract:
Using silk fibroin (SF) as a co-absorbed carrier to load the icariin (ICA) on the interface of porous β-tricalcium phosphate (β-TCP), the SF-ICA/β-TCP composites were abtained. The microstructure and porosity of the SF-ICA/β-TCP composite were maintained. The release tests show that the ICA release in composite can be controlled by loading amount. High release (2.80×10-4 mg/mL to 7.00×10-4 mg/mL) or low release (5×10-6 mg/mL to 1.0×10-5 mg/mL) of the ICA has been detected and the cumulative release is 5.2×10-3 mg or 7.0×10-5 mg, respectively. The cell proliferation have and scanning electron microscopy observation has displayed no indicated significant difference between the ICA loaded or blank SF/β-TCP composite. However, there is high expression of alkaline phosphatase activity in the ICA loaded SF/β-TCP composite. The high ICA loaded β-tricalcium phosphate may have a potential application in bone repair in vivo.
Using silk fibroin (SF) as a co-absorbed carrier to load the icariin (ICA) on the interface of porous β-tricalcium phosphate (β-TCP), the SF-ICA/β-TCP composites were abtained. The microstructure and porosity of the SF-ICA/β-TCP composite were maintained. The release tests show that the ICA release in composite can be controlled by loading amount. High release (2.80×10-4 mg/mL to 7.00×10-4 mg/mL) or low release (5×10-6 mg/mL to 1.0×10-5 mg/mL) of the ICA has been detected and the cumulative release is 5.2×10-3 mg or 7.0×10-5 mg, respectively. The cell proliferation have and scanning electron microscopy observation has displayed no indicated significant difference between the ICA loaded or blank SF/β-TCP composite. However, there is high expression of alkaline phosphatase activity in the ICA loaded SF/β-TCP composite. The high ICA loaded β-tricalcium phosphate may have a potential application in bone repair in vivo.
2017, 34(11): 2586-2592.
doi: 10.13801/j.cnki.fhclxb.20170220.004
Abstract:
Oxidation of sodium alginate (OSA) with high molecular weight and different oxidation degree was prepared by water-ethanol and water-n-propanol system, then the poly-acrylamide (PAM) cross-linked network structure was introduced. The OSA/PAM composite hydrogel was obtained by the two-step method. The effects of the volume fraction of HCl on the molecular weight of OSA as well as the influence rules of the amount and reaction time of oxidant (sodium periodate NaIO4) on the oxidation degree were investigated under different reaction conditions.The results show that the molecular weight of oxidized sodium alginate can reach 170 000 when the volume fraction of hydrochloric acid is 24vol% in water-n-propanol system. Adjusting the addition of NaIO4 and the reaction time can control the variety of oxidation degree of OSA in the range of 10%-85%. Based on this, the swelling and mechanical experiments of OSA/PAM composite hydrogels were studied, showing that the swelling rate of OSA/PAM composite hydrogel with 10% degree of oxidation is 1 777% after 48 h and the breaking strength is 0.11 MPa. In addition, with the increase of the degree of oxidation of OSA, the swelling rate of OSA/PAM composite hydrogel increases and the tensile strength decreases.
Oxidation of sodium alginate (OSA) with high molecular weight and different oxidation degree was prepared by water-ethanol and water-n-propanol system, then the poly-acrylamide (PAM) cross-linked network structure was introduced. The OSA/PAM composite hydrogel was obtained by the two-step method. The effects of the volume fraction of HCl on the molecular weight of OSA as well as the influence rules of the amount and reaction time of oxidant (sodium periodate NaIO4) on the oxidation degree were investigated under different reaction conditions.The results show that the molecular weight of oxidized sodium alginate can reach 170 000 when the volume fraction of hydrochloric acid is 24vol% in water-n-propanol system. Adjusting the addition of NaIO4 and the reaction time can control the variety of oxidation degree of OSA in the range of 10%-85%. Based on this, the swelling and mechanical experiments of OSA/PAM composite hydrogels were studied, showing that the swelling rate of OSA/PAM composite hydrogel with 10% degree of oxidation is 1 777% after 48 h and the breaking strength is 0.11 MPa. In addition, with the increase of the degree of oxidation of OSA, the swelling rate of OSA/PAM composite hydrogel increases and the tensile strength decreases.
2017, 34(11): 2593-2597.
doi: 10.13801/j.cnki.fhclxb.20170222.005
Abstract:
In order to prepare hybrid nanostructure composite with magnetocaloric effect, combining with the superior characteristics of chitosan (CS) and collagen (Col) as the organic matrix, the soluble calcium salt and soluble phosphate as the precursor of inorganic phase nano hydroxyapatite (nHAP), and the soluble salt and soluble ferrous salt as precursor to inorganic phase superparamagnetic nano Fe3O4 particles were used to prepare Fe3O4-CS-Col-nHAP composite scaffold by in situ fabrication and freeze-drying technique. The composition and morphology of Fe3O4-CS-Col-nHAP composite scaffold and the distribution of nano particles were characterized by FTIR spectroscopy, XRD and SEM. And the magnetic energy of the scaffold was tested by physical property tester (PPMS). The results show that Fe3O4-CS-Col-nHAP composite scaffold presents a homogeneously interconnected macroporous structure which has an everage size of around 100-150 μm and the porosity is about 95%. And the low crystallinity of nHAP crystals and nano Fe3O4 particles are uniformly distributed in the organic matrix. The nano Fe3O4 particles prepared by in situ fabrication has super paramagnetic properties, with the increase of magnetic nano particles, the magnetic saturation strength is enhanced. The saturation magnetization intensionsity of Fe3O4-CS-Col-nHAP composite scaffold is about 0.025 emu/g. Therefore, the hybrid nanostructure Fe3O4-CS-Col-nHAP composite scaffold prepared by in situ fabrication and freeze-drying technique has good magnetocaloric effect, and is promising for bone repair application in bone tissue engineering.
In order to prepare hybrid nanostructure composite with magnetocaloric effect, combining with the superior characteristics of chitosan (CS) and collagen (Col) as the organic matrix, the soluble calcium salt and soluble phosphate as the precursor of inorganic phase nano hydroxyapatite (nHAP), and the soluble salt and soluble ferrous salt as precursor to inorganic phase superparamagnetic nano Fe3O4 particles were used to prepare Fe3O4-CS-Col-nHAP composite scaffold by in situ fabrication and freeze-drying technique. The composition and morphology of Fe3O4-CS-Col-nHAP composite scaffold and the distribution of nano particles were characterized by FTIR spectroscopy, XRD and SEM. And the magnetic energy of the scaffold was tested by physical property tester (PPMS). The results show that Fe3O4-CS-Col-nHAP composite scaffold presents a homogeneously interconnected macroporous structure which has an everage size of around 100-150 μm and the porosity is about 95%. And the low crystallinity of nHAP crystals and nano Fe3O4 particles are uniformly distributed in the organic matrix. The nano Fe3O4 particles prepared by in situ fabrication has super paramagnetic properties, with the increase of magnetic nano particles, the magnetic saturation strength is enhanced. The saturation magnetization intensionsity of Fe3O4-CS-Col-nHAP composite scaffold is about 0.025 emu/g. Therefore, the hybrid nanostructure Fe3O4-CS-Col-nHAP composite scaffold prepared by in situ fabrication and freeze-drying technique has good magnetocaloric effect, and is promising for bone repair application in bone tissue engineering.
Tribological properties of graphene oxide/polyethylene glycol composites applied on artificial joint
2017, 34(11): 2598-2604.
doi: 10.13801/j.cnki.fhclxb.20170303.001
Abstract:
The tribological properties of graphene oxide(GO), polyethylene glycol (PEG) and different proportions of the GO/PEG composites were researched through pin and disc experiment, and the lubrication effect of PEG intensified by GO was investigated in UHMWPE-CoCrMo artificial joint materials. The structure and properties of GO/PEG composites were studied by FTIR, XRD and Laser Roman spectrometer in detail.The results show that the GO/PEG composites including 0.85wt% GO and 40wt% PEG have good lubrication effect, the average friction coefficient achieves 0.015 under the condition of 0.024 m/s sliding speed and 4.2 MPa load. GO is dispersed in PEG solution homogeneously, and the lubrication effect of GO/PEG composites can be improved significantly by the strong interfacial interactions between both components.
The tribological properties of graphene oxide(GO), polyethylene glycol (PEG) and different proportions of the GO/PEG composites were researched through pin and disc experiment, and the lubrication effect of PEG intensified by GO was investigated in UHMWPE-CoCrMo artificial joint materials. The structure and properties of GO/PEG composites were studied by FTIR, XRD and Laser Roman spectrometer in detail.The results show that the GO/PEG composites including 0.85wt% GO and 40wt% PEG have good lubrication effect, the average friction coefficient achieves 0.015 under the condition of 0.024 m/s sliding speed and 4.2 MPa load. GO is dispersed in PEG solution homogeneously, and the lubrication effect of GO/PEG composites can be improved significantly by the strong interfacial interactions between both components.
2017, 34(11): 2605-2613.
doi: 10.13801/j.cnki.fhclxb.20170327.001
Abstract:
The alkali-activated metakaolin ground granulated blast fumace slag(GGBFS) and granite were used as cementitious material and aggregate, respectively, to prepare geopolymer concrete. And SEM-EDS and microhardness test were conducted to investigate the microstructure, distribution around the aggregate surface, and mechanical properties of the bond zone between geopolymer paste and aggregate. Test results indicate that an interfacial transition zone (ITZ) exists in the bond zone between geopolymer gel and aggregates. The ITZ includes crack and N-A-S-H gel, whose chemical composition is different from geopolymer gel. The distribution of ITZ around aggregate surface is not uniform, since the ITZ near soffit of aggregate has a weaker microstructure and a lower hardness than those on upper and side surfaces of aggregate. With the increase in the liquid/solid ratio and the dimension of aggregate, the width of crack in ITZ at aggregate soffit increases and the thickness of N-A-S-H gel decreases, meanwhile changes of mixture and aggregate dimension have no obvious effect on the microstructure and the strength of ITZ at upper and side interface around aggregate, which indicates a significant inhomogeneity. It can be concluded from test results that the interface between geopolymer gel and aggregate at aggregate soffit will be the weak zone of geopolymer concrete.
The alkali-activated metakaolin ground granulated blast fumace slag(GGBFS) and granite were used as cementitious material and aggregate, respectively, to prepare geopolymer concrete. And SEM-EDS and microhardness test were conducted to investigate the microstructure, distribution around the aggregate surface, and mechanical properties of the bond zone between geopolymer paste and aggregate. Test results indicate that an interfacial transition zone (ITZ) exists in the bond zone between geopolymer gel and aggregates. The ITZ includes crack and N-A-S-H gel, whose chemical composition is different from geopolymer gel. The distribution of ITZ around aggregate surface is not uniform, since the ITZ near soffit of aggregate has a weaker microstructure and a lower hardness than those on upper and side surfaces of aggregate. With the increase in the liquid/solid ratio and the dimension of aggregate, the width of crack in ITZ at aggregate soffit increases and the thickness of N-A-S-H gel decreases, meanwhile changes of mixture and aggregate dimension have no obvious effect on the microstructure and the strength of ITZ at upper and side interface around aggregate, which indicates a significant inhomogeneity. It can be concluded from test results that the interface between geopolymer gel and aggregate at aggregate soffit will be the weak zone of geopolymer concrete.
2017, 34(11): 2614-2623.
doi: 10.13801/j.cnki.fhclxb.20170301.001
Abstract:
Cheap micron grade CaCO3 whisker was incorporated into the millimeter grade steel fiber and polyvinyl alcohol (PVA) fiber hybrid fiber reinforced cement-based composites (HyFRCC). The influence of CaCO3 whisker on mechanical behaviors, failure pattern and size effect of thin HyFRCC slabs was studied. The micro morphology of the composites was observed using SEM. The experimental results show that the thin slabs demonstrate good flexural performance, better pseudo strain hardening and multiple cracking behaviors than beams with addition of whisker. And the HyFRCCs including CaCO3 whisker are more efficient in reducing the size effect sensitivity on flexural strength. The micromorphology observation verifies that the hybrid fiber system incorporating CaCO3 whisker can inhibit the crack propagation at different scales. The study indicates that the steel fibers and PVA fibers can be replaced partly with cheap CaCO3 whiskers to produce HyFRCC, which shows good adaptability to fabricate slab element. And the dual goals of mechanical performance optimization and economy efficiency increase are both achieved.
Cheap micron grade CaCO3 whisker was incorporated into the millimeter grade steel fiber and polyvinyl alcohol (PVA) fiber hybrid fiber reinforced cement-based composites (HyFRCC). The influence of CaCO3 whisker on mechanical behaviors, failure pattern and size effect of thin HyFRCC slabs was studied. The micro morphology of the composites was observed using SEM. The experimental results show that the thin slabs demonstrate good flexural performance, better pseudo strain hardening and multiple cracking behaviors than beams with addition of whisker. And the HyFRCCs including CaCO3 whisker are more efficient in reducing the size effect sensitivity on flexural strength. The micromorphology observation verifies that the hybrid fiber system incorporating CaCO3 whisker can inhibit the crack propagation at different scales. The study indicates that the steel fibers and PVA fibers can be replaced partly with cheap CaCO3 whiskers to produce HyFRCC, which shows good adaptability to fabricate slab element. And the dual goals of mechanical performance optimization and economy efficiency increase are both achieved.
2017, 34(11): 2624-2630.
doi: 10.13801/j.cnki.fhclxb.20170309.001
Abstract:
In order to study the mechanism of the rubber effect on drying shrinkage of cement based materials, rubberized mortars were chosen as the study object. Capillary tension theory was used in the study to analysis the factors that influence the drying shrinkage of mortars. The mercury intrusion method was used to study the porosity of rubberized mortars, and the elastic modulus and the drying shrinkage tests were done as well. The results show that rubber especially that of small size can reduce the elastic modulus of cement mortars and increase the porosity and drying shrinkage of mortars. Based on the test results, KE is defined as the reduction factor of rubber on elastic modulus of mortar and Kh is defined as the increase factor of rubber on micropores (< 50 nm). δmr is defined as the rubber effect on mortar drying shrinkage, which is fitting according to KE and Kh.
In order to study the mechanism of the rubber effect on drying shrinkage of cement based materials, rubberized mortars were chosen as the study object. Capillary tension theory was used in the study to analysis the factors that influence the drying shrinkage of mortars. The mercury intrusion method was used to study the porosity of rubberized mortars, and the elastic modulus and the drying shrinkage tests were done as well. The results show that rubber especially that of small size can reduce the elastic modulus of cement mortars and increase the porosity and drying shrinkage of mortars. Based on the test results, KE is defined as the reduction factor of rubber on elastic modulus of mortar and Kh is defined as the increase factor of rubber on micropores (< 50 nm). δmr is defined as the rubber effect on mortar drying shrinkage, which is fitting according to KE and Kh.
2017, 34(11): 2631-2641.
doi: 10.13801/j.cnki.fhclxb.20170301.003
Abstract:
The quasi-static tensile tests were conducted to investigate the effects of various volume contents of short carbon fiber, steel fiber, alkali-resistant glass fiber and prestress on the tensile performance of 5 layers basalt textile reinforced cementitious matrix composite (BTRC). The experimental results indicate that short carbon and glass fibers can increase the crack stresses of both matrix and BTRC, which increase with increasing volume fraction of short carbon fibers. The applied prestress induces compressive stress in the cementitious matrix, such that the crack stress of BTRC is improved significantly. Both the short fibers and prestress can increase ultimate load and toughness, while the ultimate strain does not change significantly. Both the ultimate load and toughness increase with increasing steel fibers content and reach the maximum values at 1.5vol% volume fraction, while both properties firstly increase and then decrease with increasing content of carbon fibers with the maximum values at 1.0vol% volume fraction. When the short carbon or steel fibers are added into the matrix with prestress, the short fiber reinforced matrix can better bear the hoop stress caused by the radial expansion of the yarns in textile after releasing the tension. So the contact and frictional forces between the textile and matrix are improved, leading to the most pronounced increase in ultimate load and toughness, as much as 50.4% and 58.9%, respectively, and in toughness as much as 84.7% and 79.5%, respectively. By adding short glass fiber, steel fiber and applying prestress to the BTRC composite, the crack numbers increase with smaller crack spacing and opening in the matrix.
The quasi-static tensile tests were conducted to investigate the effects of various volume contents of short carbon fiber, steel fiber, alkali-resistant glass fiber and prestress on the tensile performance of 5 layers basalt textile reinforced cementitious matrix composite (BTRC). The experimental results indicate that short carbon and glass fibers can increase the crack stresses of both matrix and BTRC, which increase with increasing volume fraction of short carbon fibers. The applied prestress induces compressive stress in the cementitious matrix, such that the crack stress of BTRC is improved significantly. Both the short fibers and prestress can increase ultimate load and toughness, while the ultimate strain does not change significantly. Both the ultimate load and toughness increase with increasing steel fibers content and reach the maximum values at 1.5vol% volume fraction, while both properties firstly increase and then decrease with increasing content of carbon fibers with the maximum values at 1.0vol% volume fraction. When the short carbon or steel fibers are added into the matrix with prestress, the short fiber reinforced matrix can better bear the hoop stress caused by the radial expansion of the yarns in textile after releasing the tension. So the contact and frictional forces between the textile and matrix are improved, leading to the most pronounced increase in ultimate load and toughness, as much as 50.4% and 58.9%, respectively, and in toughness as much as 84.7% and 79.5%, respectively. By adding short glass fiber, steel fiber and applying prestress to the BTRC composite, the crack numbers increase with smaller crack spacing and opening in the matrix.
